WEBVTT 00:06.890 --> 00:08.120 Welcome back. 00:08.420 --> 00:14.600 Now our eye is starting to come along, but now we have to start thinking about how to handle ranged 00:14.600 --> 00:15.440 attackers. 00:15.440 --> 00:19.220 So we have a whole branch on our behavior tree to deal with. 00:19.250 --> 00:24.410 Now, let's say we have an enemy and we have our player controlled character aura. 00:24.860 --> 00:30.290 We know that our enemies will approach Aura until they're a good distance away, at which point they 00:30.290 --> 00:37.430 can start to attack and they're going to be launching projectiles or doing distance based spells and 00:37.430 --> 00:38.120 so on. 00:38.120 --> 00:41.690 But there are some considerations that need to be made. 00:41.720 --> 00:47.780 For one, distance alone is not enough to check what happens if there are obstacles in the way. 00:47.810 --> 00:53.810 If our enemies just stop and start firing obstacles at a wall just because aura is on the other side 00:53.810 --> 00:56.090 of it, they're going to look very dumb. 00:56.120 --> 00:59.510 Now let's take a look at this situation from the top. 00:59.540 --> 01:00.830 Here's a top view. 01:00.860 --> 01:05.600 We have our enemy and aura, and here's some obstacle in the way. 01:05.630 --> 01:11.150 We know that if the enemy fires a projectile, it's simply going to hit the obstacle. 01:11.160 --> 01:13.920 So what kind of behavior would we rather see? 01:13.950 --> 01:20.250 It'd be nicer if our enemy was smart enough to move just a little bit out of the way so that it could 01:20.250 --> 01:23.460 hit aura from just around the corner of the obstacle. 01:23.610 --> 01:28.950 That means it could move down here or it could move up here and hit aura from there. 01:29.130 --> 01:34.200 So how do we program the enemy's AI so that it's smart enough to do this? 01:34.230 --> 01:39.600 One way to solve this problem is with the use of unreal engine's environment query system. 01:39.780 --> 01:43.770 What we can do is we can create something called an environment query. 01:43.800 --> 01:47.880 When we run an environment query, we make use of a generator. 01:47.970 --> 01:54.090 The environment query system has several different types of built in generators that generate a set 01:54.090 --> 01:56.910 of locations or actors around. 01:56.910 --> 02:01.960 Some point we refer to these locations or actors as items. 02:01.980 --> 02:09.390 The system can then ask questions about those items by running a series of user defined tests. 02:09.570 --> 02:16.620 Based on these tests, the items can be scored and our environment query will choose the best item filtering 02:16.620 --> 02:17.700 out all the others. 02:17.700 --> 02:21.540 That did not score as well on the tests that we performed. 02:21.570 --> 02:28.740 For example, we may run a test that checks to see if each item can see the target by performing a line. 02:28.740 --> 02:35.760 Trace those who hit obstacles that might be in the way will not score as favorably as those who hit 02:35.760 --> 02:36.670 the character. 02:36.690 --> 02:42.930 After filtering out all of the items that can't see the character, we have items left that can and 02:42.930 --> 02:45.750 we can only consider these moving forward. 02:45.780 --> 02:51.120 Now we can run additional tests to see which of these remaining items is the best one. 02:51.150 --> 02:56.530 For instance, we can check the distance to the character and choose the closest item. 02:56.550 --> 03:02.580 Once we've determined which of these items is the best item, we can then set a blackboard key to that 03:02.580 --> 03:07.830 item and do whatever we wish in the behavior tree, such as move to that location. 03:08.040 --> 03:13.710 This is just one example of how to use the environment query system and it's how we'll ensure that our 03:13.710 --> 03:19.860 ranged attackers can move to a good location where they can see the player and attack from a distance. 03:19.860 --> 03:22.840 And we'll start setting this up in the videos to come. 03:22.890 --> 03:24.060 I'll see you soon.